The present invention relates to compressors that are used in vehicle air conditioners.
A typical vehicle air conditioner has a refrigerant circuit, which includes a compressor, an evaporator and other devices. The evaporator, which lowers the temperature of the passenger compartment, is connected to an inlet of the compressor by a suction pipe. The compressor compresses refrigerant gas by reciprocating pistons in cylinder bores. The compressor also includes a valve plate, which has suction ports and discharge ports. Each suction port has a suction valve flap and each discharge port has a discharge valve flap. Each flap selectively opens and closes the corresponding port. Specifically, as a piston reciprocates, refrigerant gas is drawn into the cylinder bore through the associated suction port while causing the associated suction valve flap to flex to an open position. The refrigerant gas is then compressed in the cylinder bore and discharged through the associated discharge port while causing the associated discharge valve flap to flex to an open position.
When the compressor is operating, the suction valve flaps are opened and closed quickly. In other words, the suction valve flaps vibrate. The vibration of the flaps generates suction pulsation of refrigerant gas that is drawn into the compressor. The suction pulsation is transmitted to the evaporator through the suction pipe. This causes the suction pipe and the evaporator to vibrate and produce noise.
Especially, a high frequency component of the suction pulsation causes the evaporator to produce annoying noise. Further, the evaporator is often located next to the front end of the passenger compartment. In this case, the noise may be transmitted to the passenger compartment.
In order to suppress suction pulsation, some prior art compressors include a suction muffler having a great volume in the housing. Other compressors are connected to an evaporator with a muffler having a large volume in between.
However, a large volume suction muffler enlarges the size of the compressor and increases suction pressure loss. Also, a muffler on the suction pipe complicates the piping of the refrigeration circuit and increases the number of parts in the circuit.